One Way Vision
One way vision film is like a vinyl with tiny holes or a micro perforated mesh. Since it is a vinyl, it can be easily printed using an eco solvent printer. The holes are far too tiny and closely spaced to affect image quality while printing. So imagine a film with a printed image on one side and a black back on the other.
Now, the human eye tends to take in a lot of information when in front of a large image. So when a person is standing on the outside, i.e. the image side of mesh film, his mind registers the overall image and not the pin holes